Self-priming dialysis filter

ABSTRACT

A medical filter ( 11 ) is constructed as a container with an interior volume in open fluid communication with a patient connection element ( 31 ) and a transport connection element ( 39 ). Filter support structure ( 13 ) mounted within the interior is structured as a thin, perforated member ( 14 ) carrying hydrophilic filter medium ( 17 ). A first flow path directs spent dialysate from the patient across the surface of the filter medium ( 17 ) to the transport connection ( 39 ). A second flow path directs fresh dialyalysate from the transport connection ( 39 ) through the filter medium ( 17 ) and the perforated support structure ( 13 ) to the patient connection ( 31 ).

PRIORITY CLAIM

This application claims the benefit of the filing date of U.S.Provisional Patent Application Serial No. 60/098,318, filed Aug. 28,1998 for “SELF-PRIMING DIALYSIS FILTER.”

TECHNICAL FIELD

This invention relates to kidney dialysis, and provides an improvedfilter system for home use dialysis procedures.

BACKGROUND ART

When a person's kidney function is about three percent (3%) of normal,the person is said to have end stage renal disease (ESRD). Continuousambulatory peritoneal dialysis (CAPD) is a medical therapy used toremove the toxins that accumulate in the blood when the kidneys stopfunctioning. Peritoneal dialysis uses the person's peritoneal lining asa filter mechanism. The patient introduces dialysis solution into theperitoneal cavity through a surgically implanted catheter. To accomplishthis form of dialysis, the patient leaves the solution in his or herperitoneal cavity for about 4 hours and then drains the solution out ofthe peritoneal cavity. During the time the dialysis solution is in thepatient's peritoneum, the toxins in the patients blood streem diffusethrough the peritoneal lining into the dialysis solution. When thesolution is drained, the toxins are flushed from the peritoneum with thefluid. After draining the fluid, the patient repeats the procedure byagain introducing fresh sterile solution into the peritoneal cavity tocontinuously remove toxins from the blood. The patient transfers thesolution in and out of the peritoneal cavity 4 or more times per day.Currently, most patients transfer about 4 times per day.

There are several problems associated with using CAPD to treat ESRD. Themain drawback is the increased risk of peritonitis. Peritonitis may becaused by infectious bacteria getting into the peritoneal cavity fromthe environment Other causes of peritonitis infection include organicmatter entering the peritoneal cavity from the environment ornon-dissolved solids entering the peritoneal cavity from the bagscontaining dialysis solution. According to United States Renal DataSystem (USRDS), there are 56% more deaths due to infection for patientsusing peritoneal dialysis therapy than for patients being treated usinghemodialysis. According to the New England Journal of Medicine,peritonitis occurs once every 15 patient-months of dialysis. Accordingto the USRDS some of the causes of peritonitis in CAPD patients are poortransfer technique, peritoneal access, less overall clearance of smalluremic toxins, and possible deleterious effects of the dialysis fluid onthe macrophage function.

A second problem associate with current CAPD procedures is theintroduction of air into the peritoneal cavity. As the patient transfersfluid to and from the peritoneal cavity, air from the lines is flushedinto the peritoneum. The air causes sharp pain in the shoulders andmuscles of the patient until it is absorbed and removed. Depending uponthe quantity of air, the pain can last from 20 minutes to several days.While air introduction is generally not life-threatening, it impactssignificantly upon the quality of life of a dialysis patient.

Current technology relies upon the patient's technique to preventintroduction of bacteria, organic matter and air into the peritoneum;however, even with proper technique every transfer exposes theperitoneum to the surrounding environment. The more transfers that areperformed, the greater the number of exposures. According to the USRDSand the New England Journal of Medicine, however, increasing the numberof transfers and the volume of fluid moved through the peritoneumcorrespondingly increases the effectiveness of toxin clearance.

DISCLOSURE OF INVENTION

A novel filter of this invention uses an absolute membrane micro-filterto screen out all bacteria and virtually all the organic matter.Currently, commercially available 0.2 micron absolute membrane filtersare considered to be satisfactory, but it is recognized that other sizesand types of filter media will also be operable for the practice of thisinvention. In practice, the filter may be attached to an implantedcatheter for an interval encompassing several transfers, using aseptictechnique. It is generally convenient and sufficient to change filtersonce per day. Once the filter has been put in place, the patient is freeto transfer solution virtually anywhere and in any situation. The filterprovides a barrier between the environment and the peritoneal cavity, aswell as a barrier between the non-dissolved solids in the dialysissolutions and the patient's peritoneal cavity. It thereby addressesdirectly the causes of peritonitis. The effects of poor technique andthe problems associated with peritoneal access are avoided to a greatextent, because the patient need perform only one unprotected connectionper several transfers (resulting in at least a 75% reduction inunprotected connections per day, assuming four transfers per day, usinga single filter.) The filter may be sized to allow for five or moretransfers per day to increase the toxin clearance. It maintains itsprotective properties throughout the day. It thus simply and efficientlyeliminates the main problems associated with peritonitis.

The filter also eliminates the main cause of introduction of air intothe peritoneal cavity. The first thing a patient does once the filter isattached is to drain the peritoneal cavity. The act of draining theperitoneal cavity primes the filter and effectively displaces any air inthe filter between the patient and the filter membrane, including anyair resident in the lines from the filter to the patient's peritonealcavity. The filter is ideally structured so that it primes in anyposition or orientation. The priming is thus unaffected by technique,and is accomplished every time the peritoneal cavity is drained. Thefilter membrane provides a barrier against the passage of air frombetween the dialysis solution bag and the filter membrane into thepatient. An air vent may be provided on the solution bag side of thefilter to allow the air from the lines to escape as the fresh solutionmoves through the filter to the peritoneal cavity.

The present invention provides a medical filter constructed as achamber, having an interior openly communicating with a patientconnection structure adapted for connection to a dialysis solution flowfixture carried by a dialysis patient. The interior is also in opencommunication with a transport connection adapted for connection toexternal dialysis solution containment apparatus, generally a supply offresh dialysis solution or a disposal container for spent dialysissolution. Support structure, mounted within the interior, is usuallystructured as a thin, perforated member, having a relatively very largesupport surface. Hydrophilic filter medium is mounted atop the supportsurface, and has a pore size capable of separating particulatematerials, including bacteria, from fresh dialysis solution. Firstchannel structure within the chamber defines a first flow path from thepatient connection across the surface of the filter medium to thetransport connection. Second channel structure within the chamberdefines a second flow path from the transport connection through thefilter medium and the perforated support structure to the patientconnection. Flow control mechanism may also be mounted within thechamber and operable to direct fluid from the patient connection throughthe first flow channel and to direct fluid from the transport connectionthrough the second flow channel.

A presently preferred embodiment of the invention comprises a containerwith an interior volume in open fluid communication with a patientconnection element and a transport connection element. Filter supportstructure is mounted within the interior volume. This structure mayinclude a plurality of filter elements arranged in approximatelyparallel stacked arrangement, whereby to define a plurality ofapproximately parallel flow paths straddling the filter elements. Eachfilter element includes first and second panel members, each having anexterior surface and an interior surface. Apertures extend between thoseexterior and interior surfaces. First and second edge members connectthe panel members at the respective interior surfaces of the panelmembers, whereby to enclose an interior fluid flow zone within thefilter element The edge members have exterior and interior surfaces andcarry ports arranged to permit liquid to pass through the first edgemember, through the flow zone between the opposed edge members and outthe second edge member. Hydrophilic filter medium is mounted to theexterior surfaces of the first and second panel members to cover theperforations. Flow control structure within the interior volume isconstructed and arranged to: (1) cause liquid introduced through thepatient connection structure to flow through the first edge member,through the flow zone, out the second edge member, and then across theexterior surfaces of the panel members to the transport connectionelement; and (2) cause liquid introduced through the transportconnection member to flow into the interior volume to surround thefilter elements, through the filter medium into the interior zone andout the ports in the first edge member to the patient connectionstructure.

The chamber may have an interior defined by a bottom portion and a coverportion. Visualizing the bottom portion as a box, the filter supportstructure is mounted within the interior. The filter support structuremay be visualized as being formed from spaced, perforated top and bottompanel members, joined by perforated edge members to define a spaceconstituting an interior flow path (or zone) between the panel members.The first channel structure within the chamber may be considered toinclude first and second segments structured and arranged so that liquidfrom the patient connection is directed by the first segment, throughthe perforated edge members and across the interior flow path to thesecond segment. The second channel structure within the chamber isstructured and arranged to direct liquid from the transport connection,around the exterior of the support structure, through the filter mediuminto the interior zone and through the perforated edge members to thepatient connection. A flow control mechanism mounted within the chambermay be structured and arranged to permit liquid flow from the secondsegment to the interior, thereby providing for washing of all surfacesof the filter medium. The bottom portion may conveniently take the formof a substantially rectilinear box, and the filter support structure maybe oriented to hold sheets of filter medium approximately parallel thedirection of flow of liquid traveling from the patient connectiontowards the transport connection.

BRIEF DESCRIPTION OF DRAWINGS

In the drawings, which illustrate what is currently regarded as the bestmode for carrying out the invention:

FIG. 1 is a diagrammatic representation of a first embodiment of theinvention;

FIG. 2 is a diagrammatic representation of a second embodiment of theinvention;

FIG. 3 is a pictorial view of a presently preferred embodiment of theinvention;

FIG. 4 is a view similar to FIG. 3, but with a cover portion removed toshown internal components;

FIG. 5 is an exploded view of the filter of FIGS. 3 and 4;

FIG. 6 is an exploded perspective view rotated to illustrate certain ofthe components shown by FIG. 5 from a different angle and to illustrateadditional components of the filter of FIGS. 3 and 4; and

FIG. 7 is a sectional view taken along the line 7—7 of FIG. 1, viewed inthe direction of the arrows.

BEST MODES FOR CARRYING OUT THE INVENTION

FIG. 1 illustrates a filter, generally 11 ,of this invention, whichincludes a tube 13 that has multiple perforations 14 in a middle portion15, being constructed of resilient material having physical propertiesselected to ensure that the tube 13 will retain its shape under a smallstress and if deformed under a higher stress, will return toapproximately its original shape once the stress has been removed.Filter material 17 is wrapped around the perforated tube 13 in a sealedrelationship, such that all of the holes 14 in the perforated portion 15are covered by a membrane of filter material 17. The filter material ishydrophilic, and allows the flow of liquid but constitutes a barrieragainst the flow of air. The holes 14 in the tube 13 are positionedwithin the region 15 between boundaries 19, 21 defined bycircumferential sealed interfaces between the filter membrane 17 and theexterior surface of the tube 13. One end 23 of the perforated tube 13 isprovided with a check valve 25 that allows flow only in a direction awayfrom the patient's peritoneal cavity. The other end 27 of the perforatedtube 13 is connected to an end cap 29. The end cap 29 has a connection31 for attaching the filter 11 to the patient (not shown). The filtermaterial, perforated tube, and check valve are encased in an outer cover33 that may be either flexible or rigid. The outer cover 33 is providedwith air vents 35 that permit the passage of air in either direction,but hydrophobic material 17 is positioned to cover the air vents so thatneither bacteria nor other particulate materials are able to enter thefilter 11. The hydrophobic material ideally comprises a 0.2 micronabsolute filter material. The outer cover is provided with a fitting,such as an end cap 37, which includes a connection 39 structuredappropriately for attaching the filter 11 to a pressure device (notshown), typically a pump conventional to CAPD procedures. The pressuredevice is preferably capable of adjusting the pressure in the filter 11selectively to either above or below the pressure in the peritonealcavity of the patient.

In a typical application, once the filter 11 is in place, with fixture31 connected to tubing installed in the peritoneal cavity of a patientand connection 39 attached to a pump and waste container in conventionalCAPD fashion, the peritoneal cavity is drained by operating the pump toreduce the pressure in the filter 11 to below the pressure in theperitoneal cavity. Fluid flows out of the peritoneum, through theperforated tube 13, through the check valve 25 and to a waste container(not shown), via connection 39. As fluid flows through the perforatedtube 13, it sweeps air out of the perforated tube 13. The vacuum causedby the flowing fluid inherently pulls any air entrapped between themembrane 17 and the perforated tube 13 out past the check valve 25 andthrough the connection 39. This air removal will occur regardless oforientation of the filter 11. Virtually no fluid from the perforatedtube will flow across the membrane and into the outer cavity 41 of thefilter 11 due to the vacuum pressure created by the pump. The flow willbe substantially out connection 39 (to the pump) and then (from thepump) to suitable waste container (typically a conventional drain bag-the pressure from the pump to the drain bag is inherently positive).When the vacuum is removed, air will not flow back into the perforatedtube 13 due to the check valve 25. The filter material is permeable towater and not air, so air can not flow through the filter material,through the perforations in the tube and into the perforated tube 13.

The usual second step of the CAPD procedure is to fill the peritonealcavity with fresh fluid. A fresh fluid supply is thus attached toconnection 39, ideally through through a pump, and the pressure of thefresh fluid supply is increased to higher than the pressure in theperitoneal cavity. The increased pressure causes the fluid to flow intothe filter 11, through connection 39 and through check valve 43 towardthe peritoneal cavity. As the fresh fluid flows into the filter 11, flowdirectly into the perforated tube 13 is blocked by the check valve 25.The fluid is diverted to flow around the filter material 17 and isforced through the filter material 17 (removing any bacteria andnon-dissolved solids) and into the perforated tube 13 through theperforations 14. The liquid flows out of the perforated tube 13 and intothe patient's peritoneum, via fixture 31. Any air entering the filterwith the fluid is also diverted to the chamber surrounding the filtermaterial. This air escapes via the air vents 35 in the outer cover 33.

The arrangement illustrated by FIG. 2 is generally similar to thatdescribed in connection with FIG. 1. The illustrated filter, generally49, is configured somewhat differently than the filter 11 (FIG. 1), butits operation is similar. As illustrated, an end cap fitting 51 connectsto tubing surgically installed to communicate with a patient'speritoneal cavity. A “Tee” fitting 53 is connected through appropriatetubing to a pump. The peritoneal cavity is drained by operating the pumpto reduce the pressure in the filter 49 to below the pressure in theperitoneal cavity. Fluid flows out of the peritoneum, through theperforated tube 55, through a first check valve 57 and through the Teefitting 53. Air is inherently swept from the filter 49 by the vacuumcaused by the flowing fluid. Virtually no fluid from the perforated tube55 flows across the filter medium 59 into the chamber 61 of the filter49. When the vacuum is removed, air will not flow back into theperforated tube 55 due to the check valve 57.

The peritoneal cavity is supplied with fresh fluid introduced to the Teeconnection 53. Fluid flow is through the connection 53, the check valve63, the chamber 61, through the filter medium 59, the perforations 65 inthe tube 55 and to the peritoneal cavity via fixture 51. The end caps67, 69, the outer cover 71 and the air vent 73 all function as describedin connection with FIG. 1, although their respective configurations areharmonized with the overall structure of the filter 49.

The filter, generally 81 illustrated by FIGS. 3 through 7 is presentlypreferred because of its compact, convenient size and shape. Moreover,the fluid flow paths with respect to the surface of the filter mediumoffer some additional therapeutical advantages to the dialysis patient.Practical filters of this design may be contained within a housingmeasuring approximately one half by two by three inches; a specificexample measuring about 0.6 inches high by 2.893 inches long by 1.943inches wide.

As best shown by FIG. 5, a housing, 82, comprises a cover portion 82Aand a box portion 82B. The interior of the box 82B is divided byinterior walls 84 to provide flow channels. Filter support structures,generally 85, are positioned in stacked arrangement within a relativelylarge chamber 86. As illustrated, a pair of filter supports 85 are heldby means of end extensions 87A of side rails 87B registered withinsupport channels 88. It is within contemplation that a single filtersupport or a greater plurality of filter supports be incorporated inother specific embodiments of the invention. In any case, appropriatefilter medium 88 (FIG. 6) may be positioned upon either or both theupper and lower surfaces 89A, 89B of the supports 85. This medium mayconveniently take the form of flat sheets of medical filtration membranematerial capable of removing fine particles, bacteria, virus and fungifrom aqueous solutions. One suitable such material is the hydrophilicpolyethersulfone membrane material sold under the trademark “Supor”® byPall Corporation, 2200 Northern Boulevard, East Hills, N.Y. 11548. Whilethis material is available with either smaller or larger pore sizes, apore size of 0.2 μm is currently preferred. In the illustrated instance,a single thickness of the filter membrane (not shown) is positionedagainst each surface 89A and 89B of both supports 85 to cover theapertures 90.

The box portion 82B includes a smaller chamber 91, which registers withan air vent 92A in the cover 82A. A resilient check valve, such as thesilicone panel 92B illustrated, is positioned within the vent 92Abeneath a dust cover 92C. This assembly permits air to escape from thechamber 91. An appropriate mechanism, such as a hydrophobic membrane(not visible) is positioned across the vent 92 A to block liquid flow.One suitable mechanism for this purpose is a single thickness of thePTFE membrane sold by Pall Corporation, 2200 Northern Boulevard, EastHills, N.Y. 11548 attached to the inner surface of the cover 82A tocover the vent 92A.

Flow control mechanism, such as the redundant check valves 93illustrated, direct dialysis solution entering from the sterile(patient) side connection 94 across the surfaces of the filter sheets 88towards the non-sterile (pump) side connection 95. In operation, spentdialysis solution drains from the patient through connection 94 intoflow channel 96 from which it is displaced through apertures 97 andacross the inner surfaces of filter medium 88 (FIG. 6), carried by thesupports 85 into flow channel 98. At the end 98A of the flow channel 98,solution advances against the closed end 93A of the first valve 93,thereby opening the port 99. Solution then flows into the valve chamber93B, causing the soft, resilient portion 93C (FIG. 4) to compress,thereby opening the flow path 93D. The second check valve 93 isoptional, but if present, operates in exactly the same fashion. Thecheck valves 93 thus function to direct the solution to flow channels100A, 100B, 100C across the outer surfaces of the filter medium 88.

As a consequence of this flow path, the surfaces of the filter medium 88are washed by flowing spent dialysis solution prior to the introductionof fresh dialysis solution, thereby diluting and removing pyrogens andendotoxins, as well as air. Solution eventually flows into the flowchannel 101, from which it eventually flows through the chamber 91 andout through the connection 95 to a suitable disposal site (usually abag.)

Fresh dialysis solution is introduced through the connection 95, fromwhich it flows into the flow channel 101, and then fills the compartment86 (FIG. 5). The check valves 93 prevent flow out of the compartment 86,except through the perforations 97. This travel path inevitably forceall of the fresh solution to pass through filter medium to the interiorof the supports 85. Except for a small volume of solution which remainstrapped in the channel 98, the fresh solution flows to the channel 96and then to the patient through the connection 94.

The chamber 91 may include structure (not shown) constructed andarranged to function as a pressure regulator for both stages of adialysis solution transfer. It is contemplated that a filter embodied asshown by FIGS. 3 through 7 will be used for a 24 hour period and thenreplaced with a similar filter. The illustrated embodiment has acapacity reasonably adequate for up to six typical cycles, although itseffective useful life may be longer under emergency circumstances.

Reference in this disclosure to features of the illustrated embodimentsis not intended to limit the scope of the appended claims, whichthemselves define the invention claimed. The invention may be embodiedin various configurations, and each of its constituent parts may bereplaced with other structures having equivalent characteristics orfunctions.

INDUSTRIAL APPLICABILITY

The filter of this invention is primarily useful for medicalapplications, and particularly in connection with CAPD procedures.

What is claimed is:
 1. A medical filter, comprising a chamber, having aninterior, a patient connection, in open fluid communication with saidinterior and adapted for connection to a dialysis solution flow fixturecarried by a dialysis patient, a transport connection, in open fluidcommunication with said interior and adapted for connection to externaldialysis solution containment apparatus; support structure, mountedwithin said interior, structured as a thin, perforated member, having asupport surface; hydrophilic filter medium mounted atop said supportsurface, having a pore size capable of separating particulate materialsfrom fresh dialysis solution; first channel structure within saidchamber defining a first flow path from said patient connection acrossthe surface of said filter medium to said transport connection; secondchannel structure within said chamber defining a second flow path fromsaid transport connection through said filter medium and said supportstructure to said patient connection; and flow control mechanism mountedwithin said chamber and operable to direct fluid from said patientconnection through said first channel structure and to direct fluid fromsaid transport connection through said second channel structure; whereinsaid second channel structure includes a portion in communication withan air vent structure constructed and arranged to release air fromsolution flowing through said interior while retaining said solutionwithin said interior.
 2. A medical filter according to claim 1, whereinsaid air vent structure includes a hydrophobic membrane positioned inthe travel path of air through said vent structure.
 3. A medical filteraccording to claim 1 comprising a chamber, having an interior, a patientconnection, in open fluid communication with said interior and adaptedfor connection to a dialysis solution flow fixture carried by a dialysispatient, and a transport connection, in open fluid communication withsaid interior and adapted for connection to external dialysis solutioncontainment apparatus; support structure, mounted within said interior,structured as a thin, perforated member, having a support surface;hydrophilic filter medium mounted atop said support surface, having apore size capable of separating particulate materials from freshdialysis solution; first channel structure within said chamber defininga first flow path from said patient connection across the surface ofsaid filter medium to said transport connection; second channelstructure within said chamber defining a second flow path from saidtransport connection through said filter medium and said supportstructure to said patient connection; and flow control mechanism mountedwithin said chamber and operable to direct fluid from said patientconnection through said first channel structure and to direct fluid fromsaid transport connection through said second channel structure; whereinsaid support structure comprises an inner conduit, with an open interiordefined by a first wall, having a first end, a second end and aperforated section between said first and second ends; said firstchannel structure is structured to accommodate flow through said innerconduit; said flow control mechanism comprises a check valve positionedat said second end, structured and arranged to permit flow from saidinner conduit through said transport connection; said inner conduit ispositioned with an outer housing structured and arranged to define saidsecond channel structure exterior of said perforated section; saidfilter medium is positioned adjacent said perforated section such thatfluid flow from said fluid passageway to said open interior must passthrough said medium; and said flow control mechanism further comprisesvalve means at said first end, structured and arranged to permit fluidflow from said second channel structure, through said perforatedsection, through said open interior and out said patient connection. 4.A medical filter according to claim 3, wherein said second channelstructure includes a portion in communication with an air vent structureconstructed and arranged to release air from solution flowing throughsaid interior while retaining said solution within said interior.
 5. Amedical filter according to claim 4, wherein said air vent structureincludes a hydrophobic membrane positioned in the travel path of airthrough said vent structure.
 6. A medical filter comprising a chamber,having an interior, a patient connection, in open fluid communicationwith said interior and adapted for connection to a dialysis solutionflow fixture carried by a dialysis patient, a transport connection, inopen fluid communication with said interior and adapted for connectionto external dialysis solution containment apparatus; support structure,mounted within said interior, structured as a thin, perforated member,having a support surface; hydrophilic filter medium mounted atop saidsupport surface, having a pore size capable of separating particulatematerials from fresh dialysis solution; first channel structure withinsaid chamber defining a first flow path from said patient connectionacross the surface of said filter medium to said transport connection;second channel structure within said chamber defining a second flow pathfrom said transport connection through said filter medium and saidsupport structure to said patient connection; and flow control mechanismmounted within said chamber and operable to direct fluid from saidpatient connection through said first channel structure and to directfluid from said transport connection through said second channelstructure; wherein said filter medium comprises thin sheet materialconfigured to cover the perforations of said support structure.
 7. Amedical filter according to claim 6, wherein said filter mediumcomprises a micro porous membrane.
 8. A medical filter according toclaim 7, wherein said membrane has a pore size of approximately 0.2 μm.9. A medical filter according to claim 7, wherein said membrane isconstructed of polyethersulfone.
 10. A medical filter according to claim9, wherein said membrane has a pore size of approximately 0.2 μm.
 11. Amedical filter comprising a chamber, having an interior, a patientconnection, in open fluid communication with said interior and adaptedfor connection to a dialysis solution flow fixture carried by a dialysispatient, a transport connection, in open fluid communication with saidinterior and adapted for connection to external dialysis solutioncontainment apparatus; support structure, mounted within said interior,structured as a thin, perforated member, having a support surface;hydrophilic filter medium mounted atop said support surface, having apore size capable of separating particulate materials from freshdialysis solution; first channel structure within said chamber defininga first flow path from said patient connection across the surface ofsaid filter medium to said transport connection; second channelstructure within said chamber defining a second flow path from saidtransport connection through said filter medium and said supportstructure to said patient connection; and flow control mechanism mountedwithin said chamber and operable to direct fluid from said patientconnection through said first channel structure and to direct fluid fromsaid transport connection through said second channel structure; whereinsaid chamber has an interior defined by a bottom portion and a coverportion, said support structure mounted within said interior is formedfrom spaced, perforated top and bottom panel members, joined byperforated edge members to define a space constituting an interior flowpath between said panel members; said first channel structure withinsaid chamber includes first and second segments structured and arrangedso that liquid from said patient connection is directed by said firstsegment, through said perforated edge members and across said interiorflow path to said second segment; and said second channel structurewithin said chamber is structured and arranged to direct liquid fromsaid transport connection, around the exterior of said supportstructure, through said filter medium into said space and through saidperforated edge members to said patient connection; and said flowcontrol mechanism mounted within said chamber is structured and arrangedto permit liquid flow from said second segment to said interior.
 12. Amedical filter according to claim 11, wherein said bottom portion is asubstantially rectilinear box and said support structure is oriented tohold sheets of filter medium approximately parallel the direction offlow of liquid traveling from said patient connection towards saidtransport connection.
 13. A medical filter according to claim 11,wherein said flow control mechanism is positioned in fluid flowcommunication with said second segment of said first channel structure,and is arranged to direct liquid from said second segment to theexterior of said support structure.
 14. A medical filter according toclaim 11, including a plurality of said support structures mounted inspaced parallel relationship within said chamber.
 15. A medical filteraccording to claim 14, wherein said bottom portion is a substantiallyrectilinear box and said support structures are each oriented to holdsheets of filter medium approximately parallel the direction of flow ofliquid traveling from said patient connection towards said transportconnection.
 16. A medical filter according to claim 14, wherein saidflow control mechanism is positioned in fluid flow communication withsaid second segment of said first channel structure, and is arranged todirect liquid from said second segment to flow parallel, between andacross the exteriors of said support structures.
 17. A medical filteraccording to claim 16, wherein said second channel structure includes aportion in communication with an air vent structure constructed andarranged to release air from solution flowing through said interiorwhile retaining said solution within said interior.
 18. A medical filteraccording to claim 17, wherein said air vent structure includes ahydrophobic membrane positioned in the travel path of air through saidvent structure.
 19. A medical filter, comprising an inner conduit, withan open interior defined by a first wall, having a first end, a secondend and a perforated section between said first and second ends; a flowchannel at said first end, structured to accommodate flow into or out ofsaid inner conduit; a check valve at said second end, structured andarranged to permit flow from said inner conduit; an enclosure for saidinner conduit, structured and arranged to define a fluid passagewayexterior said perforated section; a filter medium positioned adjacentsaid perforated section such that fluid flow from said fluid passagewayto said open interior must pass through said medium, said medium beinghydrophilic and capable of blocking bacterial-sized particles; and valvemeans at said first end, structured and arranged to permit fluid flowfrom said open interior but to direct fluid flowing in the oppositedirection into said fluid passageway.
 20. A medical filter, comprising acontainer with an interior volume in open fluid communication with apatient connection element and a transport connection element; filtersupport structure mounted within said interior volume and including aplurality of filter elements arranged in approximately parallel stackedarrangement, whereby to define a plurality of approximately parallelflow paths straddling said filter elements, each said filter elementincluding first and second panel members, each having an exteriorsurface and an interior surface with apertures extending between saidexterior and interior surfaces, first and second edge members connectingsaid panel members at the respective interior surfaces of said panelmembers, whereby to enclose an interior fluid flow zone within saidfilter element, said edge members having exterior and interior surfacesand carrying ports arranged to permit liquid to pass through said firstedge member, through said flow zone between opposed said edge membersand out said second edge member, hydrophilic filter medium mounted tothe exterior surfaces of said first and second panel members to coversaid apertures; and flow control structure within said interior volumeconstructed and arranged to: cause liquid introduced through saidpatient connection element to flow through said first edge member,through said zone, out said second edge member, and then across saidexterior surfaces of said panel members to said transport connectionelement; and cause liquid introduced through said transport connectionelement to flow into said interior volume to surround said filterelements, through said filter medium into said interior zone and outsaid ports in said first edge member to said patient connection element.21. A medical filter according to claim 20, further including a channelstructure having a portion in communication with an air vent structureconstructed and arranged to release air from a solution flowing throughsaid interior volume while retaining said solution within said interiorvolume.
 22. A medical filter according to claim 21, wherein said airvent structure includes a hydrophobic membrane positioned in the travelpath of air through said vent structure.
 23. A medical filter accordingto claim 20, wherein said filter medium comprises thin sheet materialconfigured to cover the perforations of said support structure.
 24. Amedical filter according to claim 23, wherein said filter mediumcomprises a micro porous membrane.
 25. A medical filter according toclaim 24, wherein said membrane has a pore size of approximately 0.2 μm.26. A medical filter according to claim 24, wherein said membrane isconstructed of polyethersulfone.
 27. A medical filter according to claim26, wherein said membrane has a pore size of approximately 0.2 μm.